In the past gravesite monuments have, for the most part, been of solid concrete, stone or metal, without any way of storing any information beyond that which is shown in the lettering on the outside of the monument.
The heavier monuments are protected against theft chiefly by being too heavy to be moved easily. The small plate monuments are too small to sell for enough money to be worth the risk of theft because of the identification printed thereon which would make convincing evidence in court.